Germany's intelligence service, the BND, is part of a US-led secret operation aimed at stopping terrorism by targeting the Daesh terrorists returning from Syria and Iraq, Der Spiegel news magazine reported on Saturday.
The BND has taken part in Operation Gallant Phoenix, along with 21 other countries, since October, according to Spiegel.
The secret unit led by a US Joint Special Operations Command centre in Jordan collects information about fighters from the extremist militia, including documents, data, DNA traces and fingerprints that were retrieved by special forces from former Daesh bastions.
Berlin had initially declined to join out of concerns that the US could use the intelligence to plan strikes against German terrorists.
Neither the German government nor BND would comment on the report.
About 950 Daesh terrorists have left Germany over the years with the intention of joining the Daesh terror group. At least 145 of them were killed either in battle or suicide attacks.
There are currently 705 people in Germany who are considered by security officials to be at risk of committing a terrorist action, more than five times as many as in 2013.
